1. Field of the Invention
The present invention relates to an information reproducing device that is capable of reproducing at least the information recorded on an information recording medium such as an optical disk, or the like,
2. Description of the Related Art
An amount of data is rapidly increased with the rapid development of the recent digital technology, and various information recording media have been developed to fit in with user's various applications. As examples of such information recording media, hard disk, optical disk, semiconductor memory, and the like can be listed.
Meanwhile, the information reproducing device, the personal computer, etc. employing these information recording media are in user's strong demand such that the user wishes to use the device not only in a room but also out of doors. As the device that assumes such mobile application, notebook mobile personal computer, mobile information terminal typified by PDA, cellular phone, mobile game device, digital still camera, digital video camera, and the like, for example, can be listed.
In case the handled contents in the mobile applications are mainly the still image or the text data, i.e., in case only a small recording capacity of the information recording medium is required, normally the semiconductor memory is often employed. The semiconductor memory possesses such merits that the memory has a small consumption power, the memory is resistant to a falling impact because no mechanism portion is provided, and the memory has a high data transfer speed. However, since the semiconductor memory has a high cost per memory capacity, such memory is unsuitable as the recording media for the contents such as the moving picture, and the like that need a large amount of data.
In contrast, the information recording medium using the optical dusk is excellent in superiority in cost per memory capacity in terms of exchangeability of the optical disk, random access performance, and productivity of the disk when manufactured as the read only media (ROM). In particular, the information recording medium using the optical disk is the mainstream of the information recording media used to record the contents such as the moving picture, and the like that need a large amount of data.
In the information reproducing device constructed to reproduce the information at least from the information recording medium using the optical dusk, a light emitted from a laser light source, for example, must be guided to the information recording medium via the optical member, an image is formed on a recording surface of the information recording medium, and it must be sensed based on a reflected light from a recording surface whether or not a minute pit formed on the recording surface in order of μm is present. Therefore, a very high alignment accuracy of a relative positional relationship between the optical member used to guide a light emitted from a light source to the information recording medium and form an image thereon and the information recording medium is needed.
Meanwhile, in the device that assumes such mobile application, the information reproducing device is always exposed to a risk of the strong impact applied when such device is dropped, or the like. In particular, the pickup is used guide a light from a light source to a recording surface of the information recording medium and transfer a reflected light from a recording surface. For this reason, a position of the pickup must be controlled at a high speed and with high precision such that the pickup is always kept at an equal distance to the recording surface of the information recording medium, as explained in detail later, and therefore the pickup has such a structure that its position can be displaced very easily (by a week force). Therefore, when a strong external force is applied to the information reproducing device by the falling impact, or the like, the pickup is displaced to exceed a normal range of position control, i.e., a normal operating range. In some cases the pickup itself, for example, is caused to hit other member and is damaged or the member such as the suspension wire, or the like for supporting the pickup, for example, suffers unrecoverable damage by the buckling deformation, or the like.
With respect to the information reproducing device in the prior art, the structures disclosed in JP-A-63-253544, JP-A-08-339564, and Patent Literature 3, for example, are known as the measure against the impact that the pickup receives.
In JP-A-63-253544, the moving portion (pickup) consisting of an objective lens, a focus coil, and a tracking coil and an objective lens driving unit having a protecting means for relaxing an impact force applied to the pickup from the outside are disclosed. According to Patent Literature 1, it is mentioned that, since a displacement of the pickup is restrained by covering the pickup with the protecting means made of a cover, a breakage of the pickup can be prevented previously even when the pickup gets an impact force caused by the collision with other mechanism elements.
In JP-A-08-339564, in the configuration that a focal length of a light source to the recording medium is adjusted by moving the objective lens supporting member (pickup), which holds the objective lens, along the optical axis direction of the objective lens, such a structure is disclosed that a displacement of the pickup is restrained by causing an engaging member provided to an outer side of the pickup to engage with a projection, or the like provided to a part of the focus coil contained in the pickup. According to Patent Literature 2, it is mentioned that there is no need to provide the cover, or the like to the pickup consequently and it can be prevented that the objective lens supporting member runs off the chassis or the objective lens collides with the recording surface of the information recording medium.
In JP-A-04-192169, such a structure is disclosed that an optical head housing portion for housing the optical head including the pickup is provided, the optical head is housed in the optical head housing portion when the information recording medium is not inserted into the device, and the optical head is fixed by a magnet in the optical head housing portion while a power supply is turned off. According to Patent Literature 3, it is mentioned that, since the optical head is housed and fixed to the optical head housing portion, a work to prevent a damage of the optical head can be omitted when a main body of the device is moved, for example, and also a dustproof effect can be achieved.
However, in the configuration shown in JP-A-63-253544, since the pickup is constructed such that it can be displaced at least in the inside of the protecting means made of the cover, the pickup when accepts the impact is displaced in the inside of the cover. However, the cover itself has an action to restrict a displacement of the pickup but has no action to absorb an impact force. In JP-A-63-253544, the case where a runaway of the optical head main body is caused by a driving motor in the magnetic circuit to move largely is taken up as the problem. In this case, since an impact force caused by the fall, or the like, for example, is quite larger than that caused by the runaway of the magnetic circuit, it is difficult to protect sufficiently the pickup itself and the peripheral mechanism of the pickup from the failure caused by such large impact force. A configuration that a buffer material is arranged further in the inside of the cover may be considered, but this configuration is unsuitable for the information reproducing device in the mobile application since reduction in size of the device becomes difficult because of an increase in size and weight of the cover.
In the case of the configuration shown in JP-A-08-339564, like the case in JP-A-63-253544, it is also difficult to protect sufficiently the pickup from the failure caused by a large impact force generated by the fall, or the like. Also, in the configuration shown in JP-A-08-339564, since a latching means is provided in a position that is away from a center of gravity of the pickup, a local stress is applied to the latching means when the pickup receives a strong impact. There is the problem about reliability.
According to the configuration shown in JP-A-04-192169, the impact that the optical head containing the pickup gets can be absorbed by optimizing the structure of the optical head housing portion to fit for a purpose, although not explicitly shown in Literature. Thus, it is expected that the pickup and its peripheral mechanism are protected from the failure caused by the large impact force generated by the fall, or the like. However, in JP-A-04-192169, since the optical head is moved horizontally in the optical head housing portion and housed, the optical head housing portion is arranged on the outside of the outermost periphery of the information recording medium such as the optical disk, or the like and thus a size of the device is increased. In particular, in the information reproducing device that assumes the mobile application, an increase in size of the device is unacceptable from a viewpoint of portability.